The catalog pg_opclass defines index access method operator classes. Each operator class defines semantics for index columns of a particular data type and a particular index access method. An operator class essentially specifies that a particular operator family is applicable to a particular indexable column data type. The set of operators from the family that are actually usable with the indexed column are whichever ones accept the column's data type as their left-hand input.
Operator classes are described at length in Section 37.14.
Table 51.33. pg_opclass Columns
| Name | Type | References | Description |
|---|---|---|---|
An operator class's opcmethod must match the opfmethod of its containing operator family. Also, there must be no more than one pg_opclass row having opcdefault true for any given combination of opcmethod and opcintype.
oid
oid
Row identifier (hidden attribute; must be explicitly selected)
opcmethod
oid
pg_am.oid
Index access method operator class is for
opcname
name
Name of this operator class
opcnamespace
oid
pg_namespace.oid
Namespace of this operator class
opcowner
oid
pg_authid.oid
Owner of the operator class
opcfamily
oid
pg_opfamily.oid
Operator family containing the operator class
opcintype
oid
pg_type.oid
Data type that the operator class indexes
opcdefault
bool
True if this operator class is the default for opcintype
opckeytype
oid
pg_type.oid
Type of data stored in index, or zero if same as opcintype